Production of ethylene-butene copolymer



Dec. 4, 1962 M. R. CINES PRODUCTION OF ETHYLENE-BUTENE COPOLYMER FiledDec. v2o, 1957 mom AUnited States Patent O 3,067,184 PRODUCTION FETHYLENE-BUTENE COPOLYMER Martin R. Cines, Bartlesville, Okla., assignorto Phillips Petroleum Company, a corporation of Delaware Filed Dec. 20,1957, Ser. No. 704,038 4 Claims. (Cl. 260-88.2)

This invention relates to the production of ethylenebutene-l copolymer.In one aspect it relates to a process for the preparation ofethylene-butene-l copolymer by a catalytic polymerization of ethylene tobutenes followed by the catalytic conversion of ethylene and butene-l tothe copolymer.

An important consideration in the production of copolymers such asethylene-butene-l copolymer is the cost of the monomers; while ethyleneis very inexpensive, butene-l is a more expensive material. Whenbutene-l is obtained by the dehydrogenation of butane the separationproblems involved increase the cost of this material. On the other hand,when butene-l is obtained by the dehydration of butanol the cost of thealcohol is the principal factor in determining the cost of the monomer.It has been found that butene-l can also be produced from ethylene, forexample by the dimerization of ethylene over ya nickel oxide catalyst.This process is described in detail in G. C. Bailey et al. U.S. Patent2,381,198, issued August 7, 1945. Since ethylene is relativelyinexpensive the dimerization reaction provides cheap source of thebutene-l monomer. The dimerization process also has the advantage thatprecise separations are not required since both the ethylene andbutene-l are used in the subsequent copolymerization reaction. There is,however, one drawback to the preparation of the butene monomer fromethylene, in that the reaction does not stop with the formation ofbutene-l, but this material is further isomerized to butene-2. Butene-2polymerizes at a relatively slow rate with ethylene and therefore doesnot participate in the copolymerization reaction to any appreciableextent. As a result any of the butene-l which is converted to butene-2in the dimerization step comprises in effect a loss of the valuablebutene-l monomer.

It is an object of this invention to provide an improved process for theproduction of ethylene butene-l copolymer.

Another object of this invention is to provide an improved process forthe polymerization of ethylene to butene-l.

Still another object of this invention is to provide an improved processfor increasing product yield in the production of ethylene-butene-lcopolymer.

These and other objects of the invention will become more readilyapparent from the following detailed de scription and discussion.

The foregoing objects are achieved broadly by polymerizing ethylene inthe presence of a nickel oxide catalyst, passing the reaction effluentcontain-ing ethylene, butene-l and butene-Z to a second polymerizationstep, selectively copolymerizing the butene-l and ethylene in saidsecond step, separating unreacted monomers from the copolymer andrecycling butene-2 to the rst polymerization reaction.

ln one aspect of the invention unreacted butene-l and ethylene arerecycled to the polymerization reaction.

The catalytic polymerization of ethylene to butene-l and butene-2 in thepresence of nickel oxide catalysts is disclosed in detail, as previouslystated, in Bailey et al., U.S. Patent 2,381,198, issued August 7, 1945.The polymerization reaction is carried out over a rather wide range oftemperature but generally not lower than about 30 F. nor above about 440F., and preferably in the range of between about 75 to about 300 F.

High pressures favor the reaction but under suitable conditions thereaction can be carried out from as low as atmospheric pressure or belowto as high as 2000 p.s.i. or above. The polymerization reaction can becarried out in either the liquid or the gas phase. Usually liquid phaseoperation is preferred since this type of operation facilitates controlof the reaction temperature. When the reaction is carried out in theliquid phase, it is desirable to provide an inert higher boilingmaterial such as a higher boiling normal paraffin or cycloparaftin whichacts as a diluent and aids in control of the polymerization temperature.The time of contact between the olen reactant and the catalyst toproduce polymerization can vary over a very wide range, that is from aslow as 30 seconds to as high as several hours.

The nickel oxide catalyst can be prepared in a number of ways. Usuallyit is preferred to use the catalyst supported on a material such askieselguhr, alumina, silicaalumina, charcoal and the like although itcan be used without a support when prepared in a suiciently activestate. In one method of preparation nickel carbonate is reduced tometallic nickel by heating to a temperature in the range of 575 to 750F. in a stream of hydrogen. The thereby reduced nickel is converted tothe polymerization catalyst by heating it to a temperature in the rangeof 750 to 1300 F. and at least partially oxidizing it with oxygen. Inanother method active catalysts are prepared by depositing the nitrateof the metal on silica-alumina, decomposing the nitrate in a stream ofnitrogen in the temperature range of 650 to 700 F. and then heating theoxide thus produced to a temperature in the range of 750 to l300 F. in astream of diluted oxygen. These and other methods of catalystpreparation are set forth in detail in Bailey et al., Patent Nos.2,381,198 and 2,581,228.

The polymerization reaction can be carried out by utilizing the catalystin a fixed bed or if desired, when carrying out the reaction in theliquid phase, a mobile catalyst can be utilized.

In addition to nickel oxide other catalysts can be used for polymerizingethylene to mixtures of butene-l and butene-2. Thus, in the copendingapplication of E. O. Box, Serial No. 676,709, led August 7, 1957, andnow abandoned, organometal compounds of the metals aluminum, gallium,indium and beryllium, supported on adsorbent materials, are employed.With this type of catalysts high yields of butenes are obtained whenoperating in the temperature range of about 320 to 420 F. with apressure of 400 to 1000 p.s.i.g. Complete details as to the catalystpreparation, operating conditions, etc., are set forth in thisapplication.

Another catalyst which can be employed in the polymerization reaction iscobalt oxide, either alone or preferably in the form of a finely dividedmetal disposed on activated carbon or the like. This catalyst, itsmethod of preparation, and the conditions employed in carrying out thepolymerization reaction are described in detail in Anderson et al., U.S.Patent 2,380,358, issued July l0, 1945.

The catalytic copolymerization of ethylene and butene-l is preferablycarried out according to a method which is described in detail in acopending application of Hogan and Banks, Serial No. 573,877, led March26, 1956, now U.S. Patent 2,825,721 (1958). This particular methodutilizes a chromium oxide catalyst containing hexavalent chromiumassociated with silica, alumina, zirconia, thoria, etc. In oneembodiment of this application ethylene and butene-l are polymerized inthe presence of a hydrocarbon diluent, for example, an acyclic,alicyclic or less preferably aromatic compound which is inert and inwhich the formed polymer is soluble. The reaction is ordinarily carriedout at a temperature between about F. and about 450 F. and usually undera pressure sutlicient to maintain the reactants and diluent at leastpartially in the liquid state. The copolymers produced by this methodare characterized by having an unsaturation which is principally eithertrans-internal or terminal vinyl, depending on the particular processconditions employed. Copolymers are also characterized by their highdensities and high percentage of crystallinity at normal atmospherictemperatures.

Other procedures which employ different catalysts are also used forpreparing the ethylene-butene-l copolymers. For example, copolymers areprepared in the presence of organometallic compounds such as triethylaluminum, plus titanium tetrachloride, mixtures of ethyl aluminumhalides with titanium tetrachloride and the like. Another group ofcatalysts which is used comprises a halide of a group IV metal such as,for example, titanium tetrachloride, silicon tetrabromide, zirconiumtetrachloride, tin tetrabromide, etc., with one or more free metalsselected from the group consisting of sodium, potassium, lithium,rubidium, zinc, cadmium, and aluminum.

The temperature required for copolymerization varies over a relativelywide range. However, usually it is preferred to carry out the reactionat a temperature between about 200 F. and about 300 P. The particulartemperature employed depends on the catalyst used and the operatingconditions employed such as pressure, space velocity, diluent-to-olefinratio etc.

The polymerization pressure is usually maintained at a sufficient levelto assure a liquid phase reaction, that is, at least about 100 to 300p.s.i.g. depending on the polymerization temperature. Higher pressuresup to 500 to 700 p.s.i.g. or higher can be used if desired. If it isdesired to carry out the process in the vapor state much lower pressuresdown to as low as atmopheric can be used. When utilizing a fixed bed thespace velocity varies from as low as about 0.1 to about 20 volumes offeed per volume of catalyst per hour with a preferred range beingbetween about l and about 6 volumes per volume per hour. When operatingwith a mobile catalyst it is desirable to maintain catalystconcentration in the reaction zone between about 0.0l and about 10percent by weight. Residence time can be from 10 minutes or less to lhours or more.

The ethylene-butene-l copolymer is formed by reacting mixturescontaining between about 2 and about 15 percent by weight, preferablybetween about and about l5 percent by weight of ethylene based on theamount of butene-l present. Usually the .relatively non-reactivebutene-Z comprises only a minor portion of the `reactant mixture, forexample the ethylene and butene-l combined usually comprise from about80 to about 95 percent by weight of said mixture.

The use of a diluent in the copolymerization reaction in general servestwo purposes. Since the reactions are usually exothermic in nature thepresence of a quantity of diluent provides a method for obtaining closecontrol of the reaction temperature. In addition copolymers formed inthe reaction or a portion thereof may be tacky in nature and lif this isthe case the presence of the diluent tends to prevent adherence of thepolymer to the walls-of the reaction vessel and the recovery equipmentwhich is used in treating the efuent from the copolymerization reaction.In general the quantity of diluent is large relative to the monomer feedmaterials. Usually the monomers constitute between about 0.1 and about25 percent by volume of the mixture and preferably between about 2 andabout 15 percent by volume.

The solvent or `diluent `employed in the polymerization reactionincludes in general the parain hydrocarbons. Among the more usefulsolvents are acyclic paraflins having about 3 and about 12 carbon atomsper molecule such as, for example, propane, isobutane, normal pentane,isopentane, isooctane, etc., and preferably those acyclic paraiiinshaving 5 to 12 carbon atoms per molecule. Also useful in thepolymerization reaction are alicyclic hydrocarbons such as cyclohexane,methylcyclohexane, etc.

Aromatic diluents are not normally used because they (or impuritiestherein) tend to shorten the catalyst life. However, if catalyst life isnot an imporant factor in the process solvents of an aromatic nature canalso be ernployed. All of the foregoing, and in addition otherhydrocarbon diluents which are relatively inert, nondeleterious and inthe liquid state at the reaction conditions can also be employed incarrying out the copolymerization reaction.

In carrying out the invention in one embodiment thereof ethylene isdimerized to a mixture comprising butene-l and butene-Zin the presenceof a catalyst, such as nickel oxide, supported on an adsorbent material.The reaction product may contain in addition to butene-l, butene-2 andunreacted ethylene a quantity of higher boiling polymers. If so it ispreferable that these higher boiling polymers be removed from thereaction eflluent. Following the removal step, the reaction effluent isintroduced to a copolymerization zone wherein ethylene-butene-lcopolymer is formed. In the course of this reaction some of the butene-Zalso copolymerizes with ethylene, however, the rate of lthe latterreaction as compared to the reaction of butene-l and ethylene is veryslow and the amount of butene-2 thus consumed is negligible. Theefliuent from the copolymerization zone is treated for the removal orseparation of copolymer `from the unreacted monomers. This can beaccomplished by any suitable means, such as by flashing. Following thisoperation the copolymer, now associated principally with solventmaterial, is further treated for the removal of the solvent to provide adry copolymer product. The flashed monomer material 'is recycled to thepolymerization zone.

In order to more clearly describe the invention and provide a betterunderstanding thereof, reference is had to the accompanying drawingwhich is a diagrammatic illustration of a combination polymerization andcopolymerization unit suitable for `carrying out the invention.Referring to the drawing ethylene gas introduced through conduit 2 iscombined with flashed monomer material through conduit 13. The combinedstreams enter polymerization reaction zone 4 wherein the olen reactantscontact a nickel oxide catalyst supported on kieselguhr under suitableconditions to provide dimerization of ethylene to butene-l and butene-Z.The quantity of butene-Z in the recycle feed stream to zone 4 ismaintained at a rate suicient to `substantially repress the formation ofany substantial amount of butene-2 in thisy zone. Therefore, the primaryreaction of the ethylene isy to form butene-l. Effluent from thereaction zone passesv through conduit 6 and enters copolymerizationreaction zone 8. At the same 'time cyclohexane diluent and chromiumoxide catalyst containing hexavalent chromium are introduced to zone 8through conduits 10 and 12 respectively. For ease of handling thecatalyst which is finely sub-divided is slurried in cyclohexane beforeit is introduced to the reaction zone. During the copolymerizationreaction the material in the reactor is maintained in a highly agitatedstate by means of mechanical mixer or other conventional mixing means(not shown).

The reaction is carried out at a temperature of about 240 F. and apressure of about 400 p.s.i.a. and for a sufficient period of time toconvert a portion of the ethylene and butene-l to copolymer. A small,insignificant amount of the butene-2 also reacts with ethylene to formcopolymer. The reaction effluent leaves zone 8 through conduit 14 andenters a flash zone 16 wherein unreacted ethylene, butene-l and butene-Zare removed, being introduced to the polymerization reaction throughconduit 18. The liquid eflluent from flash zone 16, comprisingessentially copolymer, cyclohexane and catalyst passes through conduit20 and is combined with additional solvent introduced through conduit22. The mixture then passes through exchanger 24 wherein the temperatureis increased, after which it is introduced to catalyst recovery zone 26.This zone may be a filter, a centrifuge or the like designed to operateat superatmospheric pressure. Separated catalyst Temperatures which isremoved through conduit 28 can be recycled to F. the reactor ordiscarded. If necessary, all or part of the Polymerization Zone (4) 100recycle catalyst can be subjected to a regeneration treat-Copolymerization Zone (8) 250 ment with oxygen for the removal ofcopolymer deposit 5 Flash Zone (16) 190 thereon during thepolymerization. The remaining re- Catalyst Removal Zone (26) 180 actioneluent, comprising a solution of copolymer in pressures cyclohexane, ispassed through conduit 30 for further P i separation and processing toprovide a dry copolymer Polymerization Zone (4) pnglfllllct (notS.hown.)' 10 Copolymerization Zone (8) 300 e preceding discussion hasbeen directed to a pre- Flash Zone (16) 30 ferred embodiment of theinvention. However, it is-not Catal St Re i Z n (26) 14 7 intended thatthis be taken in any limiting sense and it y Inova o e is within thescope of the invention to carry out the proc- Ethylene Dmel'zln (N CkelOxide CUL) ess with various modications. Thus, for example, any ElhylcncFeed Rate lb /hr 285i of the catalysts previously mentioned can beemployed in Bntcnc 2 Feed Rate d'0 n 198 the polymerization andcopolymerization reactions. Also, Ethylene Space Veloc'ify- 'Vivi/ln."5000 it is within the scope of the invention to carry out the Pressure ns i g" 240 polymerization reaction by utilizing a mobile catalyst asTemperatnrgl; 10o

Well as a catalyst disposed in a fixed bed. Thus, for ex- 2O ample, thepolymerization reaction can be carried out Ethylene-Bufene-ICOPOYWeI'ZaO with nickel oxide or other catalyst in a finely dividedform Ethylene Feed Rato lbi/lii. `2492 in the presence of a diluent withprovision for a suitable Butened Feed Rate d0 605 means for removing thecatalyst from the eilluent stream Bum-,6 2 Feed Rate d0 289 andreturning it to the reaction Zone, such as, by pro- Cyclohexane FeedRate d0 29,721 viding a liquid cyclone in this stream. copolymerConcentration in The following example is presented in illustration ofReactor Wtpercent" 5 7 one embodiment of the invention applied on acommer- Catalyst Concentration in Reactor do 0 7 Cial Soae- Pressurep.s.i.g 300 Example 30 Temperature F 250 Ethylene is polymerized in thePresence of a Cyclo Having thus described the invention by providing ahexane dituont and a nickel OXld Catolyst Supported on specific examplethereof it is to be understood no undue Siloa olufotna Prepared byfeouloe I Hckel carbonate to limitations or restrictions are to be'drawn by reason theremetalllo Illoke't followed by oxldlzmg m a Streamof Oxy' 35 of and that many variations and modifications are Within Eendiluted Wlth mtfogeothe scope ofthe invention.

The eluent from the polymerization reaction along I clninit withadditional ethylene is copolymerized in the presence 1 A process whichCompiises polymorizlng ethylene, 0f a Catalyst Comprising about 2-5Percent by Weight of in a polymerization zone, to form butenes;recovering, chromium aS ChrOIIliUm OXide, COltaiTlDg about 2-2 Pol'- 40from said polymerization zone, a mixture comprising l- CCD by Weight ofhexavalent chromium, aSSOCaed With butene, Z-butene, and ethylene;passing said mixture to silica alumina (weight ratio 9:1), prepared byimpregnata copolymerization zone maintained under copolymerizaing silicaalumina With a solution of chromium oxide foltion conditions and therebycausing ethylene in said mixlowed by drying an activation of dry air atgradually inture to copolymerize with l-butene in said mixture to form anormally solid copolymer as a product of the process; recovering, fromsaid copolymerization zone, a fracprocessed in a series of operationscorresponding to those tion Comprising QZ'buteHe; and Supplying eaidfraCtIOn t0 Shown in the acconinanying drawing said polymerization zone,whereby formation of 2-butene in said polymerization zone is suppressed.

EXAMPLE 5o 2. A process according to claim l wherein the ethylene ispolymerized in said polymerization zone at a temperature in the range 30to 430 F. in the presence of a Fresh raadt@ Poiymenmnon zone@ 2,160nickel oxide catalyst and the copolymerization is con-RecinfSfllnggyiengn-lnn- Wt percent ducted in said copolymerization zoneat a temperature Composition-Ethylene in the range to 450 F. in lthepresence of a chromium oxide catalyst. Cyclonexo'na 3. A process whichcomprises polymerizing ethylene Poltoizstiinzfnlm t6) in apolymerization zone to form butenes; withdrawing, linterna if from saidpolymerization zone, an eiuent comprising lcreasing temperature up to950 F. 45

The ellluent from the copolymerization reaction is F lows llr-a-em dobutene, 2-butenc, ethylene, and polymers higher boiling Make-npoycioiiexmie'ioilimenzanon zone (ii 20, 5gg than butenes; removing thehigher boiling polymers from said effluent; passing a resulting mixtureof ethylene and butenes free of higher boiling polymers to acopolymeriza- Catalyst to Copolymcrization Zone (12) Emuent FromCopolymerization Zone (14) Composition-Ethylene wt. percent.. 2. 2

d0 tion zone maintained under copolymerizing conditions Cycioiiex'n" oand thereby causing ethylene in said mixture to copolym- I; erize withl-butene in said mixture to form a normally ninuent From Fiasii Zone(2o)solid copolymer as a product of the process; recovering,Comgteg'mthylenem d i from said copolymerization Zone, a fractioncomprising Butenezlfl: 2-butene; and supplying said fraction to saidpolymerizagtcifane I tion zone; whereby formation of 2-butene in saidpolym- Copoiym'eerization zone is suppressed.

porcona- 4. A process which comprises polymerizing ethylene,

than butenes; removing the higher boiling polymers from `said euent;passing a resulting mixture of ethylene and butenes, fr ee of `higherboiling polymers, to a copolymerizartion lzone maintained undercopolymerizing conditionsrancl thereby causing ethylene in said mixtureto copo'lyrnerize with lbutene in said Vmixture to form a normally solidcopolymer which is recovered from the copolymerization Zone euent as aproduct of the process; recovering also from said copolymerization zoneeffluent a fraction comprising ethylene, l-butene, and 2-butene; andsupplying said fraction to said polymerization Zone, whereby formationof 2-butene in said polymerization zone is suppressed.

References Cited in the le of Vthis patent UNITED .STATES PATENTSAnderson et al July l0, 1945 Bailey et al. Aug. 7, 1945 Field et al.Oct. 12, 1954 Hogan et a1. Mar. 4, 1958 Fritz June 2, 1959 FORElGNPATENTS Belgium Dec. 6, 1955

1. A PROCESS WHICH COMPRISES POLYMERIZING ETHYLENE, IN A POLYMERIZATIONZONE, TO FORM BUTENES; RECOVERING, FROM SAID POLYMERIZATION ZONE, AMIXTURE COMPRISING 1BUTENE, 2-BUTENE, AND ETHYLENE; PASSING SAID MIXTURETO A COPOLYMERIZATION ZONE MAINTAINED UNDER COPOLYMERIZATION CONDITIONSAND THEREBY CAUSING ETHYLENE IN SAID MIXTURE TO COPOLYMERIZE WITH1-BUTENE IN SAID MIXTURE TO FORM A NORMALLY SOLID COPOLYMER AS A PRODUCTOF THE PROCESS; COMPRISING 2-BUTENE; AND SUPPLYING SAID FRACTION TO TIONCOMPRISING 2-BUTENE; AND SUPPLYING SAID FRACTION TO SAID POLYMERIZATIONZONE, WHEREBY FORMATION OF 2-BUTENE IN SAID POLYMERIZATION ZONE ISSUPPRESSED.